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Unformatted text preview: MicroBiology Lab Midterm Experiment 1: Media Preparation and Sterilization Terms: 1. complex medium- composed of digests of chemically undefined substances such as yeast and meat extracts. 2. defined medium- one for which a precise chemical composition is known. 3. broth- liquid medium 4. solid medium- usually agar 5. agar- extracted from Rhodophyta , the red algae; after being heated to 100C it will solidify at 40-42C and will not melt again until 80-90C. 6. plates- solid media in Petri dishes 7. deeps- test tubes containing solid medium; used for anaerobic growth 8. slants- test tubes containing solid medium solidify at an angle. Types of Sterilization-sterilization- the killing or removal of all living organisms & their viruses from a growth medium. 1. Autoclaving- common method of sterilization; sealed device that allows the entrance of steam under pressure; moist heat facilitates killing of all microorganisms including endospores ; 121C at 15 psi for 15 minutes. 2. Dry heat sterilization- kills by oxidations effects- flaming 3. Hot-air sterilization- placed in an oven and heated to 170C for 2 hours 4. Filtration- a filter with pores too small for the passage of microorganisms but large enough to allow passage of the liquid or gas.- filter is a tough disc composed of cellulose acetate or cellulose- physical removal of bacteria 5. Cold-Sterilizers- Gaseous chemosterilizers- ethylene oxide is released into a chamber where it circulates for 4 hours. 6. Electromagnetic radiation- -UV- damages the DNA (thymine dimers) leading to the death of exposed organisms; only sterilizes surfaces-Ionizing radiation- causes ions and other reactive molecules to be produced and these reactive molecules can degrade or alter biopolymers such as DNA and protein. Autoclaving Liquid media and other heat- resistant items Dry-heat sterilization(flaming) Inoculating loops Hot-air sterilization glassware Cold-sterilization (Gaseous chemosterilizers) Heat sensitive: Petri dish, plastic syringe Filtration Heat-sensitive liquids or gasses Radiation Food and medical supplies 3 Types of Solid Media 1. Nutrient Agar(Dehydrated)- Beef Extract, Peptone, Agar 2. Tryptic Soy Agar(Dehydrated)-Tryptone, Soytone, Sodium Chloride, Agar 3. Sabouraud Dextrose Agar(Dehydrated)- Neopeptone, Dextrose, Agar Experiment 2: Culturing Microorganisms from the Environment Terms: 1. pathogenic- disease-causing for humans; minority of microorganisms 2. non-pathogenic- non-disease causing; majority 3. nosocomial- hospital-acquired infections Experiment 3: Hand Washing Terms: 1. infectious dose- the number of microorganisms or viruses sufficient to establish an...
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This note was uploaded on 03/30/2008 for the course BIOL 2051 taught by Professor Brininstool during the Fall '07 term at LSU.
- Fall '07